5 RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL - select RAND method
9 #include <openssl/rand.h>
11 void RAND_set_rand_method(const RAND_METHOD *meth);
13 const RAND_METHOD *RAND_get_rand_method(void);
15 RAND_METHOD *RAND_OpenSSL(void);
19 A B<RAND_METHOD> specifies the functions that OpenSSL uses for random number
20 generation. By modifying the method, alternative implementations such as
21 hardware RNGs may be used. IMPORTANT: See the NOTES section for important
22 information about how these RAND API functions are affected by the use of
25 Initially, the default RAND_METHOD is the OpenSSL internal implementation, as
26 returned by RAND_OpenSSL().
28 RAND_set_default_method() makes B<meth> the method for PRNG use. B<NB>: This is
29 true only whilst no ENGINE has been set as a default for RAND, so this function
30 is no longer recommended.
32 RAND_get_default_method() returns a pointer to the current RAND_METHOD.
33 However, the meaningfulness of this result is dependent on whether the ENGINE
34 API is being used, so this function is no longer recommended.
36 =head1 THE RAND_METHOD STRUCTURE
38 typedef struct rand_meth_st
40 void (*seed)(const void *buf, int num);
41 int (*bytes)(unsigned char *buf, int num);
42 void (*cleanup)(void);
43 void (*add)(const void *buf, int num, int entropy);
44 int (*pseudorand)(unsigned char *buf, int num);
48 The components point to the implementation of RAND_seed(),
49 RAND_bytes(), RAND_cleanup(), RAND_add(), RAND_pseudo_rand()
51 Each component may be NULL if the function is not implemented.
55 RAND_set_rand_method() returns no value. RAND_get_rand_method() and
56 RAND_OpenSSL() return pointers to the respective methods.
60 RAND_METHOD implementations are grouped together with other
61 algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in B<ENGINE> modules. If a
62 default ENGINE is specified for RAND functionality using an ENGINE API function,
63 that will override any RAND defaults set using the RAND API (ie.
64 RAND_set_rand_method()). For this reason, the ENGINE API is the recommended way
65 to control default implementations for use in RAND and other cryptographic
70 L<rand(3)>, L<engine(3)>